I am interested in how planets and satellites have evolved to their current states, and what explains the spectacular planetary diversity we see. For instance, why do the Earth and Ganymede possess magnetic fields at the present day, while Venus and Europa do not? Why is tiny Enceladus geologically active, while its neighbour Mimas is dormant? To answer questions like this requires a combination of spacecraft observations and geophysical models.

I am spending a lot of my time using observations of the icy satellites of Jupiter and Saturn to work out their current state and history. For instance, the fact that the geologically-active hot-spot on Enceladus is at the south pole may not be a coincidence: the satellite may have rolled over on its side. If correct, this hypothesis tells us about the structure of the interior of Enceladus. One of the factors that makes these satellites more complicated and interesting than the terrestrial planets is that their thermal evolution depends on their orbits (because of tidal heating) as well as radioactive decay.

Some of my work involves modeling the thermal evolution of planets through time. One constraint on these models is the presence or absence of a global magnetic field: the core has to be cooling rapidly to sustain a dynamo. The reason Venus lacks a dynamo is that it is not cooling down fast enough (unlike the Earth, Venus doesn’t have plate tectonics – probably because it is very dry).